1. Field of the Invention
The invention relates to a machine tool and more particularly to a machine tool for cutting metal.
2. Background Discussion
New machine concepts, the increasing use of high-speed work spindles and the development of enhanced cutting tools have led to a fast increase of the cutting performance of modem machine tools in recent times. This also has led to a corresponding increased production of chips as well as an increased consumption of flushing and cooling liquids. In addition, the structure of the chips has also changed due to the use of high-speed work spindles, particularly due to the much higher cutting speeds. These factors result in increased requirements with respect to the collecting systems for the chips and liquids. Particularly when light metal workpieces are machined with high-speed work spindles, large amounts of chips are produced, which are collected together with the correspondingly increased amounts of flushing and cooling liquids in a pan provided below the work area of the machine.
A collecting system for chips and liquids on a machine tool has already been developed, the collecting system having a pan provided below the work area of the machine tool and having an inclined bottom as a collecting container for the resulting chips and liquids. The pan is provided with a transversely extending groove in the connecting area to the stand or bed of the machine, and a conveyor element consisting of a helical spiral rotating in the groove for conveying the chips collected in the groove to a chip outlet provided in a pan wall. The liquid collected in the pan flows through a drainage provided in the other pan wall into a collector disposed below it from which it is usually removed for treatment and cleaning. To avoid an undesired entry of chips into said collector, a perforated pipe section surrounding the driving side part of the tube spindle, having a tight fitting tolerance, is arranged in the drainage area so that chips adhering to the inner wall of the pipe section are taken along by the rotating conveyor spiral. With extremely high cutting performances and a possibly intermittent operation of the collecting system, the formation of chip clusters interspersed with liquid could not always be prevented, and caking of liquid components and chips often occurred. This hindered an effective removal of all generated substances and, in particular, resulted in problems during restart after extended standstill times.
Accordingly, there is a need for a machine tool for cutting metal with an improved collecting system for chips and liquids. The present invention satisfies these needs and provides related advantages as well.
It is a primary purpose of the invention to increase the efficiency of a collecting system for chips and liquids of a machine tool and to obtain an enhanced separation of the liquid even during extremely high chip production.
According to the invention, the purpose is satisfied in that an elongated screen element extends over at least part of the length of the conveyor element and terminates at or opens toward the liquid collector and is provided in the inner cavity of the helical conveyor element.
The screen element, which is efficaciously formed as a screen tube, will prevent chips from entering the inner cavity of the conveyor spiral. The chips are taken to the collector by the liquid flowing into the outlet. The liquids deposited together with the chips will drop through the screen tube, whereby an effective separation of the liquids from the chips is obtained while the length of the screen tube ensures a sufficiently large screen surface.
According to an efficacious embodiment of the invention the screen tube is fixedly connected to the conveyor spiral and rotatable together with it, its outlet side end protruding in a perforated tube section disposed above the liquid collector and being either fixed to the outer side of the spiral so as to rotate with it or surrounding the spiral in a stationary manner. In the latter case, chips adhering to the inner wall of the tube and possibly to the perforations are wiped away by the rotational movement of the spiral.
According to a further development of the invention, the screen tube is not rotatable and is positioned on the inside of the conveyor spiral with little tolerance. In this embodiment a wiping effect, for possibly adhering chips, is obtained by the rotational movement of the conveyor spiral. In this embodiment the screen tube may be provided with sieve openings only in its upper region so that the entering liquid will flow to the outlet on the continuous bottom part. For the non-rotary support of the screen tube, rod elements or axes are provided on one or both tube ends. The rod elements or axes are fixed to one or both side walls of the pan or to another stationary component to keep the pipe centered in the inside of the spiral.